This invention relates to a non-contact power supply device separately comprising a secondary unit from a primary unit of a coupling transformer for driving a load such as decoration lamps, and more particularly, to a non-contact power supply device which is able to control and change an output voltage of the secondary unit and the load solely from the inside of the premises without need for a user to go outside.
There exists a non-contact power supply device capable of separately forming a secondary unit and a primary unit of a coupling transformer. Typically, such a non-contact power supply device is used for driving electric decoration lamps, electric message boards, sign boards, and the like (hereafter xe2x80x9celectric decorationxe2x80x9d or xe2x80x9cloadxe2x80x9d). A non-contact power supply device, the primary unit is provided inside of a house or building (premises) while the secondary unit is provided at outside. A power plug of the primary unit is plugged into a power socket of an indoor commercial power supply, while the secondary unit is provided outdoor.
Then, both the primary and secondary units of the transformer are arranged to face each other through, for example, a glass window or a wall in between to supply electric power from the inside to the outside, thereby providing electric power to an outside load connected to the secondary unit outside. Thus, in the non-contact power supply device, the indoor commercial power supply can be use for the outdoor load while separating the indoor from the outdoor without needs of opening the door or window.
In the conventional technology, for example, when electric decoration such as decoration lamps (loads) are connected to the secondary unit, a control circuit will be required to change the lighting patterns of the decoration lamps. Thus, such a control circuit is established in the secondary unit connected to the decoration lamps.
However, in the case where the control circuit for changing the lighting patterns of the decoration lamps is provided to the secondary unit, an operation switch for the control circuit also has to be established on the secondary unit. Consequently, the user has to go outside to handle the operation switch, which is inconvenient. In other words, the non-contact power supply device, although being able to use the indoor commercial power supply for the decoration lamps while keeping the premises closed, it involves a problem where the user has to go outside to change the lighting patterns. It is especially troublesome and inconvenient in the winter season, when the non-contact power supply device is used as a power supply for the decoration lights on a Christmas tree.
Further, in the conventional non-contact power supply device, when only a small amount of current (or no current) flows through the secondary unit such as when the load connected thereto is small (or no load), there arises a problem that an output voltage will increase to exceed the allowable level. More specifically, if the load connected to the secondary unit is small such as the control circuit noted above, an excessive voltage will be produced in the secondary unit, which may cause damages in the load.
Therefore, the present invention is made to solve the problems associated with the non-contact power supply device in the conventional technology mentioned above.
It is an object of the present invention to provide a non-contact power supply device which is capable of controlling an object (load) connected to a secondary unit of a coupling transformer from a primary unit of the coupling transformer without needs for a user to go outside of premises.
It is another object of the present invention to provide a non-contact power supply device which is capable of preventing an output voltage of the secondary unit from becoming excessively large by automatically controlling the output voltage in response to changes in the load connected to the secondary unit.
It is a further object of the present invention to provide a non-contact power supply device which is capable of producing an alternating current (AC) power at outside of the premises which is identical to the commercial AC power supply available inside of the premises.
In one aspect of the present invention, the non-contact power supply device includes a primary unit and a secondary unit of a coupling transformer which are separated from one another in use and transfers electric power from the primary unit to the secondary unit through electromagnetic induction in a non-contact fashion.
In the non-contact power supply device, the secondary unit of the coupling transformer includes a second rectifying smoothing circuit for rectifying and smoothing a high frequency alternating current flowing through a secondary winding based on a high frequency alternating current flowing through a primary winding of the primary unit in order to produce a DC (direct current) output voltage, a voltage hold circuit for maintaining the DC output voltage from the second rectifying smoothing circuit for a predetermined time length, a constant voltage output circuit for producing a stabilized constant voltage based on the DC output voltage from the voltage hold circuit, a control circuit provided with the constant voltage from the constant voltage output circuit for controlling an operation of a load, and a drive signal generation circuit for supplying a drive signal to the control circuit when the output voltage from the second rectifying smoothing circuit becomes smaller than a predetermined voltage.
In the non-contact power supply device, the primary unit of the coupling transformer includes an operation circuit for either stopping the high frequency alternating current flowing through the primary winding or changing the frequency of the high frequency alternating current flowing through the primary winding to decrease the output voltage of the second rectifying smoothing circuit smaller than the predetermined voltage for generating the drive signal by the drive signal generation circuit.
According to the non-contact power supply device of the present invention, the high frequency alternating current flows through the secondary winding of the secondary unit in response to the high frequency alternating current flowing through the primary winding of the primary unit.
The alternating current flowing in the secondary winding is rectified and smoothed by the second rectifying smoothing circuit, and is output as a DC voltage from the second rectifying smoothing circuit.
The output voltage of the second rectifying smoothing circuit is maintained by the voltage hold circuit. Based on the output voltage from the voltage hold circuit, a constant voltage is produced by the constant voltage output circuit. The constant voltage is provided to the control circuit as a power source.
When the alternating current flowing in the primary winding is stopped or its frequency is changed by the operation circuit in the primary unit, the output voltage from the second rectifying smoothing circuit of the secondary unit becomes smaller than the predetermined voltage. As a result, a drive signal is generated from the drive signal output circuit which is provided to the control circuit, thereby changing the load such as lighting patterns of the decoration lamps.
Consequently, a signal for controlling the load can be output to the control circuit in the secondary unit by the operation circuit in the primary unit in the coupling transformer. In other words, the control circuit in the secondary unit can be operated from the primary unit within the premises. Thus, the user can handle the object (load) connected to the secondary unit from the primary unit without needs to go outside of the premises. This is especially useful in the cold season or under bad weather condition.
Further, in the non-contact power supply device, the load is a set of decoration lamps and the control circuit stores a plurality of lighting patterns for the decoration lamps in a memory and changes the lighting patterns in response to the drive signal from the drive signal generation circuit. Accordingly, the lighting patterns of the decoration light connected to the secondary unit can be operated and switched from the primary unit.
Further, in the non-contact power supply device, the primary unit of the coupling transformer is comprised of a first rectifying smoothing circuit for producing a direct current by rectifying and smoothing an alternating current (AC) power source, and a drive circuit which oscillates for converting a direct current from the first rectifying smoothing circuit to the high frequency alternating current so that the high frequency alternating current flows through the primary winding.
In this arrangement, the operation circuit stops the oscillation or changes the oscillation frequency in the drive circuit so as to stop the oscillation or to change the oscillation frequency of the high frequency alternating current flowing through the primary winding, thereby changing the output voltage of the second rectifying smoothing circuit in the secondary unit of the coupling transformer smaller than the predetermined voltage.
According to this non-contact power supply device, the alternating current input to the primary unit is once rectified and smoothed by the first rectifying smoothing circuit and converted into a direct current. The direct current is then converted to a high frequency alternating current by the drive circuit which flows through the primary winding. By electromagnetic induction of the high frequency alternating current flowing through the primary winding, an alternating current flows through the secondary winding of the secondary unit. Accordingly, a DC voltage is generated from the second rectifying smoothing circuit based on the alternating current in the secondary unit.
Thus, by the operation circuit, where the oscillation by the drive circuit is stopped or its oscillation frequency changed, the alternating current flowing in the primary winding is also stopped or its frequency changed. This makes the output voltage of the second rectifying smoothing circuit smaller than the predetermined voltage. Thus, the drive signal from the signal output circuit is provided to the control circuit. In this manner, the drive signal can be supplied to the control circuit of the isolated secondary unit by driving the operation circuit of the primary unit to change the load such as the lighting pattern of the decoration lamps.
In addition, in the non-contact power supply device, the secondary winding of the coupling transformer includes a resonance circuit so that the oscillation frequency in the primary unit and a resonance frequency in the secondary unit become identical to one another. As a result, because the impedance of the secondary winding is decreased, the alternating current can easily flow in the secondary winding, thereby efficiently transferring the electric power from the primary unit to the secondary unit.
Further, in the non-contact power supply device, the primary unit includes a frequency compensation circuit for changing the oscillation frequency of the high frequency alternating current flowing through the primary unit to be different from the resonance frequency of the secondary unit when a distance between the primary unit and the secondary unit installed together is small.
Thus, when the space between the primary unit and the secondary unit is small, the frequency compensation circuit changes the oscillation frequency of the primary unit from the resonance frequency of the secondary unit. In general, when the distance between the primary winding and secondary winding of the coupling transformer is small, the coupling coefficient between the two windings will increase, thus, the output voltage of the secondary winding will rise abnormally.
However, in the power supply device of the present invention, the oscillation frequency of the primary unit is changed from the resonance frequency of the secondary unit by the frequency compensation circuit. Therefore, it is able to prevent the abnormal voltage from being generated in the output voltage in the secondary winding, which is in turn able to prevent accidents such as fire breakouts. Also, since the frequency compensation circuit is installed in the primary unit, the operation for the compensation circuit can be conducted at the primary unit.
Further, in the non-contact power supply device of the present invention, the primary unit of the coupling transformer is comprised of a first rectifying smoothing circuit for producing a direct current by rectifying and smoothing an alternating current (AC) power supply, and a drive circuit which oscillates for converting a direct current from the first rectifying smoothing circuit to the high frequency alternating current so that the high frequency alternating current flows through the primary winding. The frequency compensation circuit changes the oscillation frequency of the high frequency alternating current produced by the drive circuit to be different from the resonance frequency of the secondary unit.
According to the non-contact power supply device, the alternating current input to the primary unit is once rectified and smoothed by the first rectifying smoothing circuit and converted to a direct current. The DC current is then converted to the high frequency alternating current by the drive circuit and supplied to the primary winding. By the electromagnetic induction of the alternating current flowing through the primary winding, the alternating current is produced in the secondary winding of the secondary unit, thereby producing an alternating voltage at the secondary winding.
The oscillation frequency in the primary unit is determined by the oscillation frequency of the drive circuit. However, since the frequency compensation circuit changes the oscillation frequency of the drive circuit, the primary unit can be operated where the oscillation frequency of that primary unit is changed from the resonance frequency in the secondary unit.
In addition, the non-contact power supply device of the present invention further includes a switch for either connecting or disconnecting an alternating current (AC) power supply to the primary unit of the coupling transformer. Thus, the AC power is supplied to the primary unit when the secondary unit is properly installed with respect to the primary unit, and the AC power is suspended when the primary unit and the secondary unit are not properly installed with one another. This allows the power supply device to operate properly depending on the manner of installation of the primary and secondary units.
Further, in the non-contact power supply device, the switch disconnects the alternating current (AC) power supply to the primary unit when the primary unit and the secondary unit of the coupling transformer are directly attached together without any intervening body. Hence, when the primary unit and the secondary unit are directly facing each other with a minimum spacing therebetween, the power supplied to the primary unit will be suspended to prevent an abnormal rise in the output voltage at the secondary winding of the coupling transformer.
Further, in the non-contact power supply device, the switch disconnects the alternating current (AC) power supply to the primary unit when the primary unit and the secondary unit of the coupling transformer are not attached face-to-face to one another. Thus, when the secondary unit is removed from the premises, the power supplied to the primary unit will be suspended even if the power plug of the primary unit is connected to the commercial power supply outlet. Therefore, the power supply device is capable of suppressing the power consumption in the primary unit.
Further, in the non-contact power supply device, a side surface of each of a primary core of the primary unit and a secondary core of the secondary unit has a C-shape where end surfaces of the primary core and the secondary core are positioned face-to-face with one another. As a consequence, the electric power can be effectively supplied to the secondary unit by efficiently interlinking the magnetic flux between the primary core and the secondary core.
Further, in the non-contact power supply device, the primary unit is provided with a casing made of high conductive non-magnetic metal, which covers a primary core other than end surfaces thereof facing the secondary unit. Accordingly, the surfaces of the primary unit except for the one facing the secondary unit is covered by the casing. Normally, the magnetic flux induced in the primary core leaks through the casing in the direction where the external sides of the casing and the bases of the primary core join together.
However, since the casing is made of the high conductive non-magnetic metal, an eddy current is generated in the direction to prevent the leaked magnetic flux when the magnetic flux passes through the casing. By the eddy current generated in this manner, the magnetic flux in the opposite direction of the leaked magnetic flux is induced in the casing, which reduces the magnetic flux interlinked between the magnetic flux leaking toward outside of the casing and the primary core. Consequently, the magnetic flux induced in the primary core effectively interlinks only with the secondary core, and thus, the electric power can be effectively transferred to the secondary unit.
In the further aspect of the present invention, the non-contact power supply device includes a primary unit and a secondary unit of a coupling transformer which are separated from one another in use and transfers electric power from the primary unit to the secondary unit through electromagnetic induction in a non-contact fashion.
The non-contact power supply device is comprised of a first coupling transformer whose primary winding is formed in the primary unit and whose secondary winding is formed in the secondary unit, a second coupling transformer where one end of its primary winding is connected to one end of the secondary winding of the first coupling transformer and other end of its primary winding is connected to one end of a secondary winding, and a resonance circuit formed in the secondary unit where one end of the resonance circuit is connected to both the primary winding and the secondary winding of the second coupling transformer and the other end of the resonance circuit is connected to the other end of the secondary winding of the first coupling transformer. The high frequency alternating current is produced between the other end of the secondary winding of the second coupling transformer and the other end of the secondary winding of the first coupling transformer.
According to the non-contact power supply device of the present invention, a current it1 flowing in the primary winding of the second coupling transformer is divided into a current ic flowing through the resonance circuit and a current ic flowing through the secondary winding of the second coupling transformer, i.e., it1=ic+it2. The voltage across the resonance circuit is Vc. At this time, a counter electromotive force Vt2 will be generated in the secondary winding of the second coupling transformer by the current it2 flowing through the secondary winding of the second coupling transformer. The sum of the voltage Vc across the resonance circuit and the counter electromotive force Vt2, i.e., Vc+Vt2, becomes the output voltage of the secondary unit.
Here, when the load connected to the secondary unit increases, the current it2 flowing through the secondary winding of the second coupling transformer as well as the current it1 flowing through the primary winding of the second coupling transformer also increase. As a result, voltages Vt1 and Vt2 at the primary winding and secondary winding of the second coupling transformer increase in proportion to the turn ratio between the two windings of the second coupling transformer.
On the other hand, when the load connected to the secondary unit decreases, the current it2 flowing through the secondary winding of the second coupling transformer as well as the current it1 flowing through the primary winding of the second coupling transformer also decrease. As a result, the voltages Vt1 and Vt2 at the primary winding and the secondary winding of the second coupling transformer decrease in proportion to the turn ratio between the two windings of the second coupling transformer.
Therefore, the current it2 of the secondary winding of the second coupling transformer changes depending upon the fluctuation of the load connected to the secondary unit. This change in the current it2 changes the voltage Vt2 of the secondary winding of the second coupling transformer in a manner to suppress the increase in the voltage Vt2. Thus, since the output voltage of the secondary unit is automatically controlled in response to the fluctuation of the load connected to the secondary unit, the load can be effectively protected from being destroyed or damaged by an excessive voltage.
Further, in the non-contact power supply device, the resonance circuit includes a resonance capacitor which forms the resonance circuit in combination with the secondary winding of the first coupling transformer and the primary winding of the second coupling transformer where capacitance of the resonance capacitor is adjusted so that a resonance frequency of the resonance circuit is equal to an oscillation frequency of a high frequency alternating current flowing through the primary unit of the coupling transformer. As a result, because the impedance of the secondary winding is decreased at the resonance frequency, the current can easily flow in the secondary winding, thereby efficiently transferring the electric power from the primary unit to the secondary unit.
Further, the non-contact power supply device includes a rectifying smoothing circuit which is connected between one end of the secondary winding of the first coupling transformer and one end of the secondary winding of the second coupling transformer for producing a DC output voltage. Hence, the non-contact power supply device can be utilized as a DC power supply. In other words, it can be utilized as a DC power source for driving electric decoration at outside of the premises.
Further, the non-contact power supply device of the present invention includes an inverter circuit having two sets of parallel connected switching circuits where each switching circuit has two serially connected switching elements wherein the inverter circuit receiving the DC output voltage from the rectifying smoothing circuit, an oscillation circuit which oscillates at a predetermined frequency, and an inverter drive circuit for turning the switching elements in the inverter circuit on and off in response to an output signal of the oscillation circuit thereby producing an alternating voltage with a frequency corresponding to the predetermined frequency at an output of the inverter circuit.
According to the non-contact power supply device, the switching elements in the inverter circuit are turned on and off by the inverter drive circuit, producing an alternating voltage having a rectangular waveform at the output of the inverter circuit. Thus, the non-contact power supply device can be utilized as an AC power supply. Furthermore, by properly selecting the oscillation frequency of the oscillation circuit, an alternating voltage with a frequency equivalent to the commercial AC power supply can be generated. Thus, the non-contact power supply device can be used as a power source for various household appliances designed for the commercial AC power supply.
Further, in the non-contact power supply device of the present invention, the primary unit of the coupling transformer includes a first rectifying circuit for rectifying the AC voltage from the commercial power supply, and a drive circuit for chopper controlling the voltage output from that first rectifying circuit and flowing an alternating current of high frequency to the primary winding of the first coupling transformer.
The secondary unit of the coupling transformer includes a second rectifying circuit for rectifying an alternating voltage output between one end of the secondary winding of the first coupling transformer and one end of the secondary winding of the second coupling transformer,. a low pass filter circuit for removing high frequency components from an output voltage of the second rectifying circuit, a zero-crossing detection circuit for generating a zero-crossing detection signal when the output voltage from the low pass filter circuit becomes approximately zero.
The secondary unit further includes an inverter circuit having two sets of parallel connected switching circuits where each switching circuit has two serially connected switching elements and receiving the output voltage from the low pass filter circuit, and an inverter drive circuit for turning the switching elements in the inverter circuit on and off in response to the zero-crossing detection signal from the zero-crossing detection circuit thereby producing an alternating voltage with a frequency equal to the commercial AC power supply at an output of the inverter circuit.
According to this non-contact power supply device, the alternating voltage output from the commercial power supply is rectified by the first rectifying circuit of the primary unit, chopper controlled by the inverter drive circuit, and flown in the primary winding of the first coupling transformer as an alternating current of high frequency. As a result, a current will flow through the secondary winding of the first coupling transformer of the secondary unit, and an alternating voltage will be generated between one end of the secondary winding of the first coupling transformer and one end of the secondary winding of the second coupling transformer.
After being rectified by the second rectifying circuit, the alternating voltage is input to the inverter circuit in the condition where high frequency components are removed therefrom by the low pass filter circuit. The output voltage of the low pass filter circuit is also input to the zero-crossing detection circuit. A zero-crossing detection signal is generated from the zero-crossing detection circuit every time when the output voltage becomes approximately zero volt.
When the zero-crossing detection signal is provided, the inverter drive circuit will turn the switching elements in the inverter circuit on and off. As a consequence, an alternating voltage with a frequency equivalent to the commercial AC power supply will be generated by the inverter circuit. Therefore, the non-contact power supply device of the present invention can be used as a power supply device for various household appliances designed for the commercial AC power supply.
Further, the non-contact power supply device includes a double pulse prevention circuit between the zero-crossing detection circuit and the inverter drive circuit for producing one zero-crossing detection signal and preventing two or more zero-crossing detection signals from being generated by the zero-crossing detection circuit within a predetermined time length.
According to this non-contact power supply device, when more than two zero-crossing detection signals are generated from the zero-crossing detection circuit within a predetermined time frame, all zero-crossing signals except the first one are prevented by the double pulse prevention circuit from being transmitted to the inverter drive circuit. Thus, even when more than two zero-crossing detection signals are produced by the zero-crossing detection circuit such as caused by noise or fluctuation of voltage waveforms, on and off timings of the switching elements of the inverter circuit are not affected, achieving an alternating voltage with high stability.